Use of prescription sleep aids nearly tripled among young adults between 1998 and 2006, according to a study released on Thursday by the healthcare business arm of Thomson Reuters.

"Insomnia, a condition traditionally associated with older adults, appears to be causing larger numbers of young adults to turn to prescription sleep aids, and to depend on them for longer periods of time," said William Marder, senior vice president and general manager for the healthcare business of Thomson Reuters, parent company of Reuters News.

A study of medical and drug claims data found a 50-percent increase in use of the drugs among all adults under 45, who also appear to be using the drugs for a longer period of time to help them fall asleep.

During the study period, the average length of time sleep aids were used by adults under 45 jumped by more than 40 percent — rising to 93 days in 2006 from 64 days in 1998.

But perhaps the most startling finding was the increase in use of sleep aids among college-age adults 18 to 24.

Use in this age group rose to 1,524 users per 100,000 in 2006, up from 599 users per 100,000 in 1998.

"I find it very worrisome that young people who should have a very strong and healthy sleep system are now finding they are turning to medication to help them get to sleep," Donna Arand, a sleep specialist at Kettering Hospital Sleep Disorder Center in Dayton, Ohio, said in a telephone interview.

Arand said she has seen a number of students seeking sleep aids because their normal sleep patterns have been disrupted in college, and she fears these adults may have trouble adjusting to a normal sleep pattern as their schedules normalize.

Rare Side Effect

Two-thirds of those in this study population were taking non-benzodiazepine hypnotics — such as Sanofi-Aventis' Ambien CR and Sepracor Inc's Lunesta.

These newer sleep aids generally have fewer side effects, but in rare cases they can cause sleep walking.

That may have led to the demise of a 51-year-old Wisconsin man who froze to death while sleep-walking barefoot in his underwear this week in below-zero cold.

The Sawyer County Sheriff's Office in Hayward, Wisconsin, said Timothy Brueggeman had Ambien at his house, and family members told the Star Tribune newspaper in Minneapolis that he had a history of sleep walking.

Chief Deputy Tim Ziegel said there was no proof that Brueggeman had taken the drug before his death but toxicology tests had been ordered.

"We do not know all the facts about what transpired," said Sanofi spokeswoman Susan Brook, noting that the circumstances of the man's death are still being investigated.

In general, she said sleep walking is a rare side effect of the drug and she cautioned that Ambien or Ambien CR should not be taken by people with a history of sleep walking, nor should they be taken with alcohol.